With the fast development of display technology, touch screen panels have gradually become popular in life. At present, depending on their constituting structures, touch panels may be classified into add on mode touch panels, on cell touch panels and in-cell touch panels. For add on mode touch panels, the touch panel and the liquid crystal display are produced separately and then attached together to form a liquid crystal display with touch function, which suffer disadvantages such as high manufacturing costs, low light transmission rate and thick modules. While for in-cell touch panels, touch electrodes of the touch panel are embedded inside the liquid crystal display, which could reduce the overall thickness of the module and also greatly decrease manufacturing costs of the touch panel, winning good graces of panel manufacturers.
At present, prior art capacitive in-cell touch panels are implemented by adding directly touch driving electrodes and touch sensing electrodes on existing TFT (Thin Film Transistor) array substrates, that is, manufacturing two layers of strip electrodes intersecting in different planes on the surface of the TFT array substrate. These two layers of ITO (Indium Tin Oxides) electrodes serve as touch driving electrodes and touch sensing electrodes of the touch panel respectively. As shown in FIG. 1, a mutual capacitance Cm is generated due to the coupling between the transversely disposed touch driving electrodes Tx and longitudinally disposed touch sensing electrodes Rx. When a finger touches the screen, the touching of finger would change the value of mutual capacitance Cm. A touch detection device detects the location of the finger's touch point by detecting the variation amount of a current corresponding to the capacitance Cm before and after touching.
As shown in FIG. 1, two kinds of mutual capacitances Cm are generated between the transversely disposed touch driving electrodes Tx and longitudinally disposed touch sensing electrodes Rx. One is a projection capacitance effective for realizing touch function (curve with arrow in FIG. 1), which changes the value of the projection capacitance when a finger touches the screen. Another is an opposite capacitance useless for realizing touch function (straight line with arrows). When touch driving electrodes and touch sensing electrodes have too large right opposite areas in vertical direction, the opposite capacitance formed at the right opposite areas will be too large relative to the projection capacitance, resulting in a large detection initial value of the touch detection device, making it impossible to accurately detect minute variation of signals of the projection capacitance after a finger touches the screen. This causes a reduced SNR of the touch screen and in turn impacts the accuracy of touch sensing in an in-cell touch panel.